1. Field of the Invention
This invention relates to the preparation and use of homogeneous mixtures of solid organic acids with solid cationic ester-based polymer flocculants.
2. Description of the Prior Art
Cationic polymer flocculants are used for sludge dewatering, in water treatment, in wastewater treatment, and for many industrial processes such as paper making. Cationic polymer flocculants are first dissolved in water to form a dilute solution and then the solution is mixed with the sludge or water to be treated. In most uses, the polymer flocculant causes flocculation of suspended solids which are concentrated and separated from the water by mechanical means. In laboratory tests, the drainage rate of the water through the suspended solids held on a filter is commonly used to measure the relative efficiency of polymer flocculants. Faster drainage rates and lower filter resistance result from the use of more efficient polymers.
It can be shown in some instances that the performance of the cationic ester-based polymer flocculants can be improved by addition of acid to the polymer solution. The resulting improvement has been attributed to reduction in hydrolysis of the ester linkage (for instance, see Cadel and Larson, U.S. Pat. No. 4,668,747), or other reactions not yet understood.
Avoiding fine particles in dry polymer flocculants is also important because the dust is troublesome to workers. Also, the fine particles produced by the manufacturing process often represent a yield loss. It would be an added benefit if a process could add an acid which also reduces the fines present in the dry product.
It is a troublesome matter to add acid to a solution of polymer in a separate step. It is advantageous if the acid can be included with the solid cationic polymer. A simple mixture of solid acid with solid cationic polymer is not optimum because the density and or particle size of common solid acids is significantly different than that of the solid cationic polymer and consequently, separation of the two can occur during shipping and handling. When solutions of non-homogeneous mixtures of acid and polymer are made, the result can be an excess of acid in one solution and a deficiency in another. This obviously will lead to unacceptable variations in product performance.
It is an object of this invention to provide a composition or mixture of solid organic acid and solid cationic polymeric flocculant which is homogeneous and does not separate under normal use and material handling conditions.
Other advantages of the present invention will become apparent to those skilled in the art from the following description, examples and appended claims.